The present invention relates to a buckle to be used in a seat belt apparatus and a seat belt apparatus which is installed in a seat of an automobile or other vehicle that employs the buckle.
Conventionally, seats of various vehicles such as automobiles are equipped with seat belt apparatuses for protecting occupants in the event of an emergency such as a vehicle collision. Such a seat belt apparatus is normally provided with a buckle in order to facilitate an occupant putting on and removing the seat belt apparatus. Generally, the buckle is latched with a tongue which is slidably supported to a seat belt, whereby the seat belt can restrain the occupant.
A buckle has been proposed in Japanese Unexamined Patent Publication No. 2001-063515 (incorporated by reference herein) in which, for latching a tongue into the buckle, a latch member pivots so that a latch portion formed at an end of the latch member is inserted into a latch hole of the tongue, the tongue is held in the state latched with the latch portion by an ejector with the biasing force of an ejector spring, and the latch member is held in the latched state by a slider to prevent the latch member from moving in a unlatching direction and a lock pin for depressing the slider in a state to prevent the movement of the latch member in the unlatching direction, while, for releasing the tongue from the buckle, the lock pin is moved by an unlatching operation with an operation button to cancel the latched state of the latch member, and the ejector causes the latch member to pivot in a unlatching direction and push out the tongue from the buckle with the biasing force of the ejector spring.
In such a buckle, because the ejector causes the latch member to pivot when releasing the tongue from the buckle, it is desired to effectively apply the biasing force of the ejector spring as an unlatching force to the latch member. For this purpose, because the biasing force of the ejector spring is applied to the end of the latch member via the ejector in the aforementioned buckle, it is conceivable to construct a straight line connecting the end (a portion to which the biasing force of the ejector spring is applied) of the latch member and the pivotal axis of the latch member in a perpendicular orientation to the moving direction of the ejector as possible.
However, to achieve this the buckle must be long in the longitudinal direction because the pivot path of the end of the latch member projects largely toward a tongue insertion opening when the latch member pivots. Alternatively, it is conceivable to simply increase the unlatching force in order to improve the releasing performance between the tongue and the buckle. However, as the unlatching force is increased the slider and the lock pin receive the increased unlatching force. To compensate this, the strength of the slider and the lock pin must be increased.
Therefore, it is difficult to effectively apply the biasing force of the ejector spring to the latch member in the conventional buckle because the conventional buckle has a limitation in making the aforementioned straight line nearly perpendicular to the moving direction of the ejector without increasing the length of the buckle in the longitudinal direction and without increasing the strength of the slider.
It is also desired to improve the comfort to occupant wearing the seat belt as much as possible.